Interpolation methods in the simulation of power electronic converters

Abstract

This thesis is devoted to the simulation of switching events in power systems and power electronics circuits. It addresses issues related to algorithms using fixed time step integration methods. In power electronic circuits simulation, the high repetitive rate of switching events causes numerical difficulties that require development of techniques to achieve an accurate representation of switching events. Various techniques are proposed in the literature to accurately determine switching instants. The thesis proposes an interpolation-extrapolation (IE) algorithm, which eliminates numerical oscillations and provides a sufficiently precise solution. The method gives accurate results even with larger time steps. The proposed method is tested in a number of circuits using electronic switches and to power electronic circuits. To solve the problems resulting from natural commutation of diode and forced commutation of transistors and Gate Turn Off Thyristors, an extension of the IE technique is proposed. Contrary to existing methods, the proposed method eliminates the need to force the semiconductors to work as pairs, or to add snubber circuits across every switch. To test the applicability of the method, it has been successfully implemented and tested in commercial packages under development at IREQ (Institut de Recherche d'Hydro-Québec)